Fertilizers are responsible for over half of global food production, but there are areas in world with nutrient deficiency and other areas of nutrient excess.
Managing mineral plant nutrients requires careful application of science and skill to meet production, environmental, and social goals.

Wednesday, December 18, 2013

Potassium chloride - the most common potash fertilizer (muriate of potash)

Potassium fertilizers are commonly used to
overcome plant deficiencies.

Potassium deficient lettuce

Where soils cannot supply the amount of K required
by crops, it is necessary to supplement this essential plant nutrient. Potash
is a general term used to describe a variety of K-containing fertilizers used
in agriculture. Potassium chloride (KCl), the most commonly used source, is
also frequently referred to as muriate of potash or MOP (muriate is the old
name for any chloride-containing salt). Potassium is always present in minerals
as a single-charged cation (K+).

Production

Deeply buried potash deposits are found
throughout the world. The dominant mineral is sylvite (KCl) mixed with halite (sodium
chloride), which forms a mixed mineral called sylvinite. Most K minerals are
harvested from ancient marine deposits deep beneath the Earth’s surface.

Mining potassium salts in Belarus

They
are then transported to a processing facility where the ore is crushed and the
K salts are separated from the sodium salts. The color of KCl can vary from red
to white, depending on the source of the sylvinite ore. The reddish tint comes
from trace amounts of iron oxide. There are no agronomic differences between
the red and white forms of KCI.

Potassium fertilizer comes in several colors, depending on their geological source

Some KCl is
produced by injecting hot water deep into the ground to dissolve the soluble
sylvinite min­eral and then pumping the brine back to the surface where the
water is evaporated. Solar evaporation is used to recover valuable potash salts
from brine wa­ter in the Dead Sea and the Great Salt Lake (Utah).

Salt beds at the Dead Sea

Chemical Properties

Property: KCl

Fertilizer analysis 0-0-60

K content approx 50%

Water solubility (20o C) 344 g/L

Solution
pH approx. 7

Agricultural Use

Potassium chloride is the most widely used K fertilizer due to
its relatively low cost and because it includes more K than most other
sources...50 to 52% K (60 to 63% K2O) and 45 to 47% Cl-.

Over 90% of global potash production is used for plant
nutrition. Potassium chloride is often spread onto the soil surface prior to
tillage and planting. It may also be applied in a concentrated band near the
seed. Since dissolving fertilizer will increase the soluble salt concentration,
banded KCl is placed to the side of the seed to avoid damaging the germinating
plant.

Potassium fertilizer (KMg-SO4)

Potassium
chloride rapidly dissolves in soil water. The K+ will be retained on
the negatively charged cation exchange sites of clay and organic matter. The Cl-
portion will readily move with the water. An especially pure grade of KCl can
be dissolved for fluid fertilizers or applied through irrigation systems.

Management Practices

Potassium chloride is primarily used as a source of K nutrition.
However, there are regions where plants respond favorably to application of Cl-.
Potassium chlo­ride is usually the preferred material to meet this need. There
are no significant impacts on water or air associated with normal application
rates of KCl. Elevated salt concentrations surrounding the dissolving
fertilizer may be the most impor­tant factor to consider.

Red potassium chloride

Non-agricultural Use

Potassium
is essential for human and animal health. It must be regularly ingested because
the body does not store it. Potassium chloride can be used as a salt substitute
for individuals on a restricted salt (sodium chloride) diet. It is used as a
deicing agent and has a fertilizing value after the ice melts. It is also used
in water softeners to replace calcium in water.

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About Me

I am a soil scientist with interest in managing plant nutrients in the best way possible. I am fortunate to be able to work in research and education to be able to accomplish this goal.
After receiving a PhD in Soil Science at the University of California (Riverside), I worked as a Research Scientist for the U.S. government, as a Professor of Soil Science, and now I work for a not-for-profit institution. It's been a wonderful experience!